The invention concerned is a tracheal tube which closes the trachea against the flow of fluids by blocking it below the glottis with a fitted cuff through which a respiratory cannula passes, beside which cranially, above the cuff, is situated an inflatable tampon-bladder of flexible material which in its filled state takes a shape different from that of the cuff.
In one of the tracheal tubes of this kind described in U.S. Pat. No. 4,235,239 the cuff in its inflated state is approximately ball-shaped and constitutes a mooring fitted to the glottis. The cuff is designed to leave the subglottal space free. Situated above the cuff a second cuff is provided, which when inflated is approximately disc-shaped and when compressed fits water-tight above the glottis near the pharyngeal cavity. With this tracheal tube the glottis is compressed between the two cuffs, so that on prolonged intubation dangerous bruising and necrosis (tissue damage due to death of parts of the membrane) may result. There is in addition the risk of luxation (sliding out) of the tube.
In U.S. Pat. No. 5,033,466 a tracheal tube is presented in which a strongly inflated cuff is fitted to the respiratory passages under pressure to create a watertight closure. Situated above the cuff a second cuff filled with foam is provided at the narrowest diameter of the glottis, so that the harder respiratory cannula does not strike against and damage it.
With the use of a single cuff the low perfusion pressure on the vascular bed of the subglottal mucosa necessitates edging forward of the cuff of the tube over the cricoid cartilage into at least the region of the upper trachea. This results on intubation in a so-called subglottal space extending from the edge of the upper cuff to the vocal cords. During intubation pharyngeal secretion heavily contaminated with bacteria can leak unhindered into the subglottal space and incubate there, accessible to treatment only with difficulty.
The subglottal secretion endangers the artificially ventilated patient in two respects.
Because of inadequate sealing at the time of placing of the cuff, in the course of ventilation secretion manages continuously to pass the cuff barrier and on into the distal tracheobronchial system, and so is responsible for the development of the majority of all the pneumoniae (lung inflammations) associated with assisted respiration.
Furthermore stasis (damming up) of the subglottal secretion readily leads after a few days to inflammatory changes in the local mucous membrane. The chronic inflammatory process can go on to substantial consequent complications, such as e.g. the development of subglottal stenoses.
In U.S. Pat. No. 4,091,816 a tracheal tube with two fluid-associated cuffs is presented. The lower cuff is bullet-shaped, inelastic and for mooring is fitted to the glottis from below. The cuffs are separated from each other by a groove so that the glottis can interpose between the two cuffs. The upper cuff lies above the glottis and can expand into the pharyngeal cavity. Use of this tube carries the danger that the glottis will be damaged by compression. The extension of the upper cuff into the pharyngeal cavity can lead to autonomic stimulation, such as e.g. vagal reflexes, and thereby prepares the way for difficulties during the protracted phase of rehabilitation in a respirator.
In U.S. Pat. No. 4,449,523 a tracheal tube is proposed in which a first cuff is inflated watertight in the respiratory passages. Separate from the cuff is a second cuff for sealing the aperture in its neck through which the respiratory cannula passes. Between the cuffs airholes are provided inside the cannula. This avoids the risk that highly contaminated secretion might be inhaled through the holes.
In EP 0 277 797 A2 an operation tube for laser operations is described. Two identically designed cuffs are placed on a respiratory cannula. Both cuffs are blocked off for the duration of the operation so that they give a watertight fit to the respiratory tract under pressure. The upper cuff is intended as a buffer against possible injury by a laser instrument. This operation tube is intended only for short-term intubation during operations. In long-term intubation there might be the risk that on account of the deliberately minimalized surface of the laser tube and the deleterious build-up of pressure on the epithelium lesions of the tracheal epithelium would quickly develop.
In DE 295 11 468 U1 and G 87 115 92.1 tracheal tubes are described having two identically designed cuffs situated separately from each other.
It is the problem of the present invention to improve a tracheal tube of the kind mentioned at the beginning to the extent that a patient can be intubated without harm over a long period with only slight risk of infection.
This object is attained according to the invention by a tracheal tube with the features of Claim 1.
By the direct union of the tampon-bladder with the distal cuff the subglottal reservoir of pathogens is practically eliminated and a narrow gap between the tracheal mucosa and the inserted item, that is, the tampon-bladder, is reduced. The direct placing of the tampon-bladder on the cuff also results in an effectually continuous passageway in this region, since the reservoir of pathogens is reduced to just the narrow gap. In principle no pathogenic reservoir results, but only a thin film of secretion.
Pharyngeal secretion is forced back into the supraglottal region and penetration into the subglottal region substantially prevented. The infective path for the microbes of the pharyngeal secretion is lengthened maximally by the inserted item and with the tampon-bladder unfolded extends from the glottis to the lower margin of the cuff. Pathogens consequently require longer for passage of the infective pathway, and in the region of the narrow gap between the device and the mucosa they can be neutralized by the defence mechanisms of the epithelium itself and penetration into the distal respiratory passages impeded. Hence the solution provided by the invention makes it possible for the first time to use the body""s own defence mechanisms for the avoidance of infections.
Since on unfolding the tampon-bladder no infectively sufficient subglottal volume of secretion remains, the risk of chronic subglottal stenosis due to inflammation can be excluded.
Since the tampon-bladder serves exclusively to fill the subglottal space, it can be applied so as to fulfil its purpose with epithelium-sparing minimal pressure. Pressure-associated necroses in the region of the subglottal mucosa can thus be avoided.
Advantageous characteristics and modes of employment of the invention are stated in the accompanying Claims.